1. Field of the Invention
The present invention relates to an injection stretch blow molding device and a molded article heating device.
2. Description of the Related Art
A blow molding system may utilize a 2-stage (cold parison) method or a 1-stage (hot parison) method.
According to the 2-stage (cold parison) method, a blow molding system is provided separately from a preform injection molding system, and the preform injection molding operation and the blow molding operation are implemented off-line. A preform (parison) that has been produced by injection molding using the injection molding system, and allowed to cool to room temperature (i.e., natural cooling) is supplied to the blow molding system. The preform supplied from the injection molding system is heated to the optimum blow temperature using a heating section, and subjected to blow molding using a blow molding section to obtain a container. The preforms are intermittently or continuously transferred in the heating section, and at least one preform is intermittently transferred from the heating section to the blow molding section. The blow molding section subjects at least one preform to blow molding to obtain at least one container (see U.S. Pat. No. 7,727,454, Japanese Patent Application Publication No. JP-A-2000-117821 and Japanese Patent Application Publication No. JP-A-2007-276327).
According to the 2-stage (cold parison) method, the blow molding cycle of the blow molding system is set independently of the injection molding cycle of the preform injection molding system, and throughput can be improved. However, the energy efficiency decreases when using the 2-stage (cold parison) method since the preform that has been cooled to room temperature is heated to the optimum blow temperature.
An injection stretch blow molding system that utilizes the 1-stage (hot parison) method is configured so that the preform injection molding operation and the blow molding operation are implemented in-line. Specifically, N preforms that have been produced by injection molding using an injection molding section are subjected to blow molding in a state in which the preforms retain heat applied during injection molding to obtain N containers. A typical blow molding system is configured so that an injection molding section, a temperature control section, a blow molding section, and an ejection section are provided at four positions on a turntable, and a preform or a container is rotated using a neck mold (see Japanese Patent Application Publication No. JP-A-53-22096). In this case, a preform that has been produced by injection molding in an upright state is transferred in the upright state, and subjected to blow molding.
According to the 1-stage (hot parison) method, since the preform that retains heat applied during injection molding is subjected to blow molding to obtain a container, the thermal energy that is required for heating the preform to room temperature to the optimum blow temperature is unnecessary. However, the blow molding cycle of the blow molding system is the same as the injection molding cycle of the preform injection molding system, and the number of preforms simultaneously produced by injection molding is the same as the number of preforms simultaneously subjected to blow molding.
The applicant of the present application developed a practical 1.5-stage injection stretch blow molding system that effectively utilizes the advantages of the 1-stage method and the 2-stage method (see Japanese Patent No. 2954858). The 1.5-stage injection stretch blow molding system is basically configured so that the preform that retains heat applied during injection molding is subjected to blow molding to obtain a container in the same manner as in the case of using the 1-stage method. However, the blow molding cycle of the injection stretch blow molding system can be reduced as compared with the injection molding cycle of the preform injection molding system, and the ratio of the number (N) of preforms simultaneously produced by injection molding to the number (M) of preforms simultaneously subjected to blow molding can be set to 3:1, for example.